I understand some people don’t feel that certain posts are worth engaging with (which is fine) but at least don’t downvote then?
I disagree, I think it’s perfectly fine for people to downvote posts without commenting. The key function of the karma system is to control how many people see a given piece of content, so I think up-/downvotes should reflect “should this content be seen by more people here?” If I think a post clearly isn’t worth reading (and in particular not engaging with), then IMO it makes complete sense to downvote so that fewer other people spend time on it. In contrast, if I disagree with a post but think it’s well-argued and worth engaging with I would not downvote, and would engage in the comments instead.
Oh, I agree that comment + downvote is more useful for others than only downvote, my main claim was that only downvote is more useful than nothing. So I don’t want there to be a norm that you need to comment when downvoting, if that leads to fewer people voting (which I think would be likely). See Well-Kept Gardens Die By Pacifism for some background on why I think that would be really bad.
Tbc, I don’t want to discourage commenting to explain votes, I just think the decision of whether that is worth your time should be up to you.